Device for axially retaining a cylindrical element and more particularly a cable

ABSTRACT

Device for axial maintenance of a cylindrical element, wherein the device includes a coupling bushing comprising external threads, first nut strips which extend axially beyond the external threads, and a first internal pressure surface. A covering nut is provided which includes a second internal pressure surface configured to engage and deform ends of the first nut strips radially indwardly and towards the cylindrical element when the cylindrical element is introduced into the coupling bushing and the covering nut. A sleeve is also provided which includes second nut strips and an external diameter which is at most equal to an internal diameter of the coupling bushing, whereby the sleeve, with the second nut strips being introduced first, is adapted to be introduced into the coupling bushing. The first internal pressure surface is configured to engage and deform ends of the second nut strips radially indwardly and towards the cylindrical element when the cylindrical element is introduced into the coupling bushing and the covering nut.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a National Stage Application of InternationalApplication No. PCT/FR01/02248, filed Jul. 12, 2001. Further, thepresent application claims priority under 35 U.S.C. § 119 of FrenchPatent Application No. 00/09608 filed on Jul. 21, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a device for axial maintenance of acylindrical element and more particularly a cable.

2. Discussion of Background Information

For fixing a cylindrical element into another element, such as forexample, an electric cable into the coupling bushing of a plug orelectricity socket, or furthermore, for example, into a conduit, a tubeor pipe in an apparatus or accessory, it is known how to use deviceswhich maintain said cylindrical element against traction efforts.

For this, a device for axial maintenance is known comprising an axialmaintenance device for a cylindrical element and more particularly for acable, comprising a coupling bushing which is threaded externally andwhich is prolonged in the axial direction by tightening nut strips, anda covering nut comprising internally a reduced pressure surface intendedto act on the ends of the nut strips of the coupling bushing and todeform them radially towards the cylindrical element previouslyintroduced into said coupling bushing after crossing said nut.

This type of device is, for example, described in the French patent2358766 or again in the European patent 0381980.

In the French patent cited above, the device furthermore comprises apacking seal and thus constitutes both a compression gland or stuffingbox.

In this device known in prior art, the packing deforms into a truncatedcone and the adhesion of the cable is active over a limited length.

Furthermore, the deformation of the packing is not well containedinternally and each device can only concern a restricted number ofelements to fix, in a relatively reduced range of diameters.

Finally, in such a device, there cannot be any strip anchoring in theelement to be held since any traction on the latter tends to separatesaid strips.

SUMMARY OF THE INVENTION

Among other things, the invention makes it possible to improve thetraction resistance performances of this type of device, especially inorder to fulfil the anti-deflagration standards relative to the domainof electrical apparatuses.

In order to do this, a device according to the invention of the typedescribed above is particularly notable in that it further comprises asleeve also provided with nut strips and whose external diameter is atmost equal to the internal diameter of the coupling bushing in whichsaid sleeve is intended to be introduced beginning by said strips withwhich it is provided. The coupling bushing is further providedinternally with a reduced pressure surface, which is intended to act onthe nut strips of the sleeve.

According to an embodiment, the pressure surface of the coupling bushingand the sleeve are dimensioned so that the strips of said sleeve anchorinto the cylindrical element during the tightening of the nut.

In order to ensure tightness, the invention envisages an embodimentwhich is provided with a tubular sealing packing intended to be insertedin final position between the cylindrical element, the sleeve and thecoupling bushing strips.

For example, in this case, the sealing packing is in two parts ofdifferent external diameters, the smallest external diametercorresponding substantially to the internal diameter of the sleeve andthe biggest diameter corresponding substantially to the internaldiameter of the coupling bushing.

A device according to the invention which remains compact and which onlyrequires a single screwing operation also makes it possible to ensure,with a single device, both the anchoring and the sealing of variouscables in a large range of diameters, which simplifies the choice of theuser, limits storage problems and raises manufacturing volumes, thusreducing production costs.

The invention also provides for a device for axial maintenance of acylindrical element, wherein the device comprises a coupling bushingcomprising external threads, first nut strips which extend axiallybeyond the external threads, and a first internal pressure surface. Acovering nut is provided which comprises a second internal pressuresurface configured to engage and deform ends of the first nut stripsradially inwardly and towards the cylindrical element when thecylindrical element is introduced into the coupling bushing and thecovering nut. A sleeve is also provided which comprises second nutstrips and an external diameter which is at most equal to an internaldiameter of the coupling bushing, whereby the sleeve, with the secondnut strips being introduced first, is adapted to be introduced into thecoupling bushing. The first internal pressure surface is configured toengage and deform ends of the second nut strips radially inwardly andtowards the cylindrical element when the cylindrical element isintroduced into the coupling bushing and the covering nut.

The cylindrical element may comprise a cable. The first and secondinternal pressure surfaces may be configured to cause the first andsecond nut strips to be anchored in the cylindrical element when thecovering nut is tightened. The first and second internal pressuresurfaces may comprise tapered surfaces. The first and second internalpressure surfaces may comprise tapered surfaces which face in oppositedirections.

The device may further comprise a tubular packing seal adapted to beinserted in, a final assembled position, between the cylindrical elementand the sleeve. The device may further comprise a tubular packing sealadapted to be inserted in, a final assembled position, between thecylindrical element and the first nut strips. The device may furthercomprise a packing seal adapted to slide over the cylindrical elementand into the sleeve. The packing seal mat comprise a first part having afirst external diameter and a second part having a different secondexternal diameter. The first diameter may be smaller than the seconddiameter, wherein the first diameter corresponds substantially to aninternal diameter of the sleeve, and wherein the second diametercorresponds substantially to the internal diameter of the couplingbushing.

The covering nut may comprise internal threads configured to threadablyengage the external threads of the coupling bushing.

The invention also provides for a method of fixing the cylindricalelement using the device described above, wherein the method comprisesarranging the coupling bushing on the cylindrical element with the firstnut strips facing in a first direction, arranging the sleeve on thecylindrical element with the second nut strips facing in a secondopposite direction, arranging the covering nut on the cylindricalelement, moving the covering nut towards the coupling bushing, engagingand deforming ends of the second nut strips radially inwardly with thefirst internal pressure surface by moving the covering nut towards thecoupling bushing, threadably engaging internal threads of the coveringnut and the external threads of the coupling bushing, and engaging anddeforming ends of the first nut strips radially inwardly with the secondinternal pressure surface by moving the covering nut further towards thecoupling bushing.

The invention also provides for a device for fixing a cable to a plug ora socket, wherein the device comprises a coupling bushing comprisingexternal threads, first strips which extend axially from one end of thecoupling bushing, and a first internal tapered pressure surface. A nutis provided which comprises internal threads and a second internaltapered pressure surface configured to engage and deform ends of thefirst strips radially inwardly. The internal threads of the nut areconfigured to threadably engage the external threads of the couplingbushing. A sleeve is provided which comprises second strips which extendaxially from one end of the sleeve. The sleeve is configured to slidewithin the coupling bushing. The first internal tapered pressure surfaceis configured to engage and deform ends of the second strips radiallyinwardly when the nut moves towards the coupling bushing.

The first and second internal tapered pressure surfaces may beconfigured to cause the first and second strips to be anchored in thecable when the nut is tightened onto the coupling bushing. The first andsecond internal tapered pressure surfaces may face in oppositedirections.

The device may further comprise a tubular packing seal adapted to beinserted between the cable and the sleeve. The device may furthercomprise a tubular packing seal adapted to be inserted between the cableand the first strips. The device may further comprise a packing sealadapted to slide over the cable and into the sleeve. The packing sealmay comprise a first part having a first external diameter and a secondpart having a different second external diameter. The first diameter maybe smaller than the second diameter, wherein the first diametercorresponds substantially to an internal diameter of the sleeve, andwherein the second diameter corresponds substantially to the internaldiameter of the coupling bushing.

The invention also provides for a method of fixing a cable to a plug ora socket using the device described above, wherein the method comprisesarranging the coupling bushing on the cable with the first strips facingin a first direction, arranging the sleeve on the cable with the secondstrips facing in a second opposite direction, arranging the nut on thecable, moving the nut towards the coupling bushing, engaging anddeforming ends of the second strips radially inwardly with the firstinternal tapered pressure surface by moving the nut towards the couplingbushing, threadably engaging the internal threads of the nut and theexternal threads of the coupling bushing, and engaging and deformingends of the first strips radially inwardly with the second internaltapered pressure surface by moving the nut further towards the couplingbushing.

The invention also provides for a device for fixing a cable to a plug ora socket, wherein the device comprises a coupling bushing comprisingexternal threads, first strips which extend axially from one end of thecoupling bushing, and a first internal tapered pressure surface. A nutcomprises internal threads and a second internal tapered pressuresurface configured to engage and deform ends of the first stripsradially inwardly. The internal threads of the nut is configured tothreadably engage the external threads of the coupling bushing. A sleevecomprises second strips which extend axially from one end of the sleeve.The sleeve is configured to slide within the coupling bushing. A tubularpacking seal is adapted to be inserted partially into the sleeve and thecoupling bushing. The first internal tapered pressure surface isconfigured to engage and deform ends of the second strips radiallyinwardly when the nut moves towards the coupling bushing.

The invention also provides for a method of fixing a cable to a plug ora socket using the device described above, wherein the method comprisesarranging the coupling bushing on the cable with the first strips facingin a first direction, arranging the sleeve on the cable with the secondstrips facing in a second opposite direction, arranging the tubularpacking seal on the cable, arranging the nut on the cable, moving thenut towards the packing seal until the second internal tapered surfaceengages the packing seal, causing the sleeve and the packing seal toslide into the coupling bushing, moving the nut towards the couplingbushing, engaging and deforming ends of the second strips radiallyinwardly with the first internal tapered pressure surface by moving thenut and the packing seal towards the coupling bushing, threadablyengaging the internal threads of the nut and the external threads of thecoupling bushing, and engaging and deforming ends of the first stripsradially inwardly with the second internal tapered pressure surface bymoving the nut further towards the coupling bushing.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be better understood and other particularities willbecome clear by reading the following description which refers to theattached drawings in which:

FIG. 1 shows an exploded view of a device according to the invention;

FIG. 2 shows an axial cross-section of the various elements to beassembled;

FIGS. 3, 4 and 5 show axial cross-sections of the device of FIGS. 1 and2, respectively before screwing the nut, at the beginning of screwingand at the end of screwing; and

FIG. 6 shows a view corresponding to FIG. 5 according to another veryslightly different embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The figures represent a device according to the invention intended tofix, in the example shown, an electric cable 1 (FIGS. 3 to 6) in a bush2 of an electrical connection system (coupling bushing of a plug ormobile plug or of an extension or connector etc.)

The device according to the invention comprises a coupling bushing 3integral with the bush 2, a sleeve 4, a packing seal 5 in rubber and aring shaped nut 6.

As shown clearly in the diagrams, the coupling bushing 3 and the sleeve4 are provided with a base 7 and a base 8 respectively, prolonged bystrips 9 and 10 respectively which protrude externally in the axialdirection. The strips 10 of the sleeve 4 are positioned for assembly, asexplained below, towards the strips 9 of the coupling bushing 3 (FIGS. 1and 2). The base 7 of the coupling bushing 3 is further provided with anexternal threading as shown in the drawings. This external threading isintended to co-operate with the internal threading of the nut 6.

At the base of its threading, the nut 6 has an internal pressure surface11 reduced, for example, in truncated form whose function will beexplained below.

In the same way, the base of the coupling bushing 3 is, on the oppositeside from the strips 9, provided with a reduced internal pressuresurface 12.

As shown clearly in the drawings, the packing 5 has two parts 5 a and 5b in steps of different external diameters.

The smallest external diameter (part 5 a) of the packing 5 correspondssubstantially to the internal diameter of the base 8 of the sleeve 4 andthe biggest diameter (part 5 b) corresponds substantially to theinternal diameter of the strips 9 of the coupling bushing 3 beforedeformation, while the external diameter of said sleeve 4 issubstantially equal to the internal diameter of the coupling bushing 3.

The drawings show clearly the way in which to assemble together thevarious elements of the device.

The elements are initially arranged as shown in FIGS. 1 and 2.

Beginning from this assembly, the sleeve 4 is introduced by its stripsinto the coupling bushing 3, and after or before, the part 5 a isintroduced into the packing 5 in the base 8 of the sleeve 4 and thecovering nut 6 is set in place on the strips 9 of the coupling bushing 3in order to be in the position of FIG. 3.

Before or after this first assembly, the cable 1 is evidently introducedthrough all the elements (2, 3, 4, 5 and 6).

Starting from the position of FIG. 3, the nut 6 is pushed which itselfpushes the packing assembly 5 and sleeve 4 until the strips 10 of thesleeve 4 are held radially by the pressure surface 12 of the couplingbushing 3 to be deformed and to be tightened onto the cable 1 as shownin FIG. 4.

Next the screwing of the nut 6 is carried out which accentuates thedeformation of the strips 10. By continuing said screwing of the nut 6,the strips 9 of the coupling bushing 3 tighten radially on the packing 5by deforming under the effect of the pressure surface 11 of said nut 6.

In the embodiment of FIGS. 1 to 5, the length of the sleeve 4 and thepressure surface 12 of the coupling bushing 3 are such that the strips10 of said sleeve 4 are anchored at the end of screwing in the cable 1as shown in FIG. 5.

In the embodiment of FIG. 6, the base 8 of the sleeve 4 is less longaxially and/or the strips 10 are shorter as well as the pressure surface12, in such a way that in this embodiment, said strips 10 do not anchorin the cable 1. Given that the differences of the sleeve and the surface12 of the coupling bushing 3 of the device of FIG. 6, relative to thesleeve 4 and the coupling bushing 3 of FIGS. 1 to 5 are essentiallydimensional, the same references have been kept on said figures.

On FIGS. 5 and 6, it can be seen that the packing 5 is perfectlycompressed by the sleeve 4 and the strips 9 of the coupling bushing 3,and furthermore it is perfectly maintained between its two ends by thestrips 9 and 10 of the coupling bushing 3 and the sleeve 4 respectively.

Compared to prior art, the invention enables a greater length of contactbetween the packing 5 and the cable 1 together with a greater volume ofdeformed packing, which increases the reliability of the sealing andretention, thus ensuring a greater reserve of elasticity to compensatefor the relaxation of plastic parts intended to compress the packing.

The strips 9 of the coupling bushing 3 act on the packing 5 and thecable 1 in a classic way whereas the strips 10 of the sleeve 4 act inthe opposite direction with, further, an anchoring or not, in the cable1 (FIGS. 5 and 6 respectively).

Furthermore it can be understood that in the embodiment of FIGS. 1 to 5,any traction on the cable accentuates the anchoring of the sleeve 4,said anchoring thus being self-blocking.

If the embodiment relates in particular to an electric cable, it canevidently concern, as explained above, any cylindrical element.

1. A device for axially maintaining a cylindrical element, the devicecomprising: a coupling bushing comprising external threads, first nutstrips which extend axially beyond the external threads, and a firstinternal pressure surface; a covering nut comprising a second internalpressure surface configured to engage and deform ends of the first nutstrips radially inwardly and towards the cylindrical element when thecylindrical element is introduced into the coupling bushing and thecovering nut; and a sleeve comprising second nut strips and an externaldiameter which is at most equal to an internal diameter of the couplingbushing, whereby the sleeve, with the second nut strips being introducedfirst, is adapted to be introduced into the coupling bushing, whereinthe first internal pressure surface is configured to engage and deformends of the second nut strips radially inwardly and towards thecylindrical element when the cylindrical element is introduced into thecoupling bushing and the covering nut.
 2. The device of claim 1, whereinthe cylindrical element comprises a cable.
 3. The device of claim 1,wherein the first and second internal pressure surfaces are configuredto cause the first and second nut strips to be anchored in thecylindrical element when the covering nut is tightened.
 4. The device ofclaim 1, wherein the first and second internal pressure surfacescomprise tapered surfaces.
 5. The device of claim 1, wherein the firstand second internal pressure surfaces comprise tapered surfaces whichface in opposite directions.
 6. The device of claim 1, furthercomprising a tubular packing seal adapted to be inserted in, a finalassembled position, between the cylindrical element and the sleeve. 7.The device of claim 1, further comprising a tubular packing seal adaptedto be inserted in, a final assembled position, between the cylindricalelement and the first nut strips.
 8. The device of claim 1, furthercomprising a packing seal adapted to slide over the cylindrical elementand into the sleeve.
 9. The device of claim 8, wherein the packing sealcomprises a first part having a first external diameter and a secondpart having a different second external diameter.
 10. The device ofclaim 9, wherein the first diameter is smaller than the second diameter,wherein the first diameter corresponds substantially to an internaldiameter of the sleeve, and wherein the second diameter correspondssubstantially to the internal diameter of the coupling bushing.
 11. Thedevice of claim 1, wherein the covering nut comprises internal threadsconfigured to threadably engage the external threads of the couplingbushing.
 12. A method of fixing the cylindrical element using the deviceof claim 1, the method comprising: arranging the coupling bushing on thecylindrical element with the first nut strips facing in a firstdirection; arranging the sleeve on the cylindrical element with thesecond nut strips facing in a second opposite direction; arranging thecovering nut on the cylindrical element; moving the covering nut towardsthe coupling bushing; engaging and deforming ends of the second nutstrips radially inwardly with the first internal pressure surface bymoving the covering nut towards the coupling bushing; threadablyengaging internal threads of the covering nut and the external threadsof the coupling bushing; and engaging and deforming ends of the firstnut strips radially inwardly with the second internal pressure surfaceby moving the covering nut further towards the coupling bushing.
 13. Adevice for fixing a cable to a plug or a socket, the device comprising:a coupling bushing comprising external threads, first strips whichextend axially from one end of the coupling bushing, and a firstinternal tapered pressure surface; a nut comprising internal threads anda second internal tapered pressure surface configured to engage anddeform ends of the first strips radially inwardly; the internal threadsof the nut being configured to threadably engage the external threads ofthe coupling bushing; a sleeve comprising second strips which extendaxially from one end of the sleeve; and the sleeve being configured toslide within the coupling bushing, wherein the first internal taperedpressure surface is configured to engage and deform ends of the secondstrips radially inwardly when the nut moves towards the couplingbushing.
 14. The device of claim 13, wherein the first and secondinternal tapered pressure surfaces are configured to cause the first andsecond strips to be anchored in the cable when the nut is tightened ontothe coupling bushing.
 15. The device of claim 13, wherein the first andsecond internal tapered pressure surfaces face in opposite directions.16. The device of claim 13, further comprising a tubular packing sealadapted to be inserted between the cable and the sleeve.
 17. The deviceof claim 13, further comprising a tubular packing seal adapted to beinserted between the cable and the first strips.
 18. The device of claim13, further comprising a packing seal adapted to slide over the cableand into the sleeve.
 19. The device of claim 18, wherein the packingseal comprises a first part having a first external diameter and asecond part having a different second external diameter.
 20. The deviceof claim 19, wherein the first diameter is smaller than the seconddiameter, wherein the first diameter corresponds substantially to aninternal diameter of the sleeve, and wherein the second diametercorresponds substantially to the internal diameter of the couplingbushing.
 21. A method of fixing a cable to a plug or a socket using thedevice of claim 13, the method comprising: arranging the couplingbushing on the cable with the first strips facing in a first direction;arranging the sleeve on the cable with the second strips facing in asecond opposite direction; arranging the nut on the cable; moving thenut towards the coupling bushing; engaging and deforming ends of thesecond strips radially inwardly with the first internal tapered pressuresurface by moving the nut towards the coupling bushing; threadablyengaging the internal threads of the nut and the external threads of thecoupling bushing; and engaging and deforming ends of the first stripsradially inwardly with the second internal tapered pressure surface bymoving the nut further towards the coupling bushing.
 22. A device forfixing a cable to a plug or a socket, the device comprising: a couplingbushing comprising external threads, first strips which extend axiallyfrom one end of the coupling bushing, and a first internal taperedpressure surface; a nut comprising internal threads and a secondinternal tapered pressure surface configured to engage and deform endsof the first strips radially inwardly; the internal threads of the nutbeing configured to threadably engage the external threads of thecoupling bushing; a sleeve comprising second strips which extend axiallyfrom one end of the sleeve; the sleeve being configured to slide withinthe coupling bushing; and a tubular packing seal adapted to be insertedpartially into the sleeve and the coupling bushing, wherein the firstinternal tapered pressure surface is configured to engage and deformends of the second strips radially inwardly when the nut moves towardsthe coupling bushing.
 23. A method of fixing a cable to a plug or asocket using the device of claim 22, the method comprising: arrangingthe coupling bushing on the cable with the first strips facing in afirst direction; arranging the sleeve on the cable with the secondstrips facing in a second opposite direction; arranging the tubularpacking seal on the cable; arranging the nut on the cable; moving thenut towards the packing seal until the second internal tapered surfaceengages the packing seal; causing the sleeve and the packing seal toslide into the coupling bushing; moving the nut towards the couplingbushing; engaging and deforming ends of the second strips radiallyinwardly with the first internal tapered pressure surface by moving thenut and the packing seal towards the coupling bushing; threadablyengaging the internal threads of the nut and the external threads of thecoupling bushing; and engaging and deforming ends of the first stripsradially inwardly with the second internal tapered pressure surface bymoving the nut further towards the coupling bushing.